The killer of Socrates: Coniine and Related Alkaloids in the Plant Kingdom.

Coniine, a polyketide-derived alkaloid, is poisonous to humans and animals. It is a nicotinic acetylcholine receptor antagonist, which leads to inhibition of the nervous system, eventually causing death by suffocation in mammals. Coniine's most famous victim is Socrates who was sentenced to death by poison chalice containing poison hemlock in 399 BC. In chemistry, coniine holds two historical records: It is the first alkaloid the chemical structure of which was established (in 1881), and that was chemically synthesized (in 1886). In plants, coniine and twelve closely related alkaloids are known from poison hemlock (Conium maculatum L.), and several Sarracenia and Aloe species. Recent work confirmed its biosynthetic polyketide origin. Biosynthesis commences by carbon backbone formation from butyryl-CoA and two malonyl-CoA building blocks catalyzed by polyketide synthase. A transamination reaction incorporates nitrogen from l-alanine and non-enzymatic cyclization leads to γ-coniceine, the first hemlock alkaloid in the pathway. Ultimately, reduction of γ-coniceine to coniine is facilitated by NADPH-dependent γ-coniceine reductase. Although coniine is notorious for its toxicity, there is no consensus on its ecological roles, especially in the carnivorous pitcher plants where it occurs. Lately there has been renewed interest in coniine's medical uses particularly for pain relief without an addictive side effect.

Prolonged ventilatory failure and flaccid quadriparesis after ingestion of poison hemlock.

INTRODUCTION: A 28-year-old man presented with acute flaccid paralysis and respiratory failure that persisted for 2 weeks after suicidal ingestion of unknown substances. METHODS: Extensive clinical, nerve, laboratory, and neuroimaging testing excluded alternative causes of this neuromuscular syndrome. Prompted by clues provided by family members, liquid chromatography time-of-flight mass spectrometry was used to investigate for the presence of poison hemlock. RESULTS: Testing of the residue in a jar used for the ingestion of a poisonous concoction confirmed the presence of the nicotinic alkaloid coniine. Analysis of patient serum suggested the presence of conhydrine. Concentrations of amitriptyline and diazepam were also found to be supratherapeutic, but only through the first few days of hospitalization. CONCLUSIONS: Herein we describe a case of reversible coma, flaccid quadriparesis, and neuromuscular respiratory failure caused by intentional ingestion of poison hemlock.

Poison hemlock determination in postmortem samples.

Poison hemlock (Conium maculatum L.) is a weed that grows rampant in many areas of North America. Forensic toxicology laboratories rarely receive requests to analyze biological specimens for the presence of poison hemlock. This report discusses two postmortem cases that were encountered over a decade apart and describes different analytical approaches that may be used to quantify coniine, a primary poison hemlock alkaloid, in biological specimens. The first case is from 2004 and involves a 27-year-old female that was found deceased in a relatively isolated area of California. Based on the presence of plant material at the scene and signs of its ingestion at autopsy, the possibility of hemlock poisoning was considered. Toxicological testing of the blood and gastric content by quantitative selected-ion monitoring Gas Chromatography/Mass Spectrometry (SIM-GC/MS) revealed the presence of coniine at concentrations of 410 ng/mL and 9300 ng/mL, respectively. The second case is from Pennsylvania and was sent for analysis in the spring of 2019. In this case, a male in his forties was found deceased in the kitchen area of a camper. Green substances, in liquid and residue forms, were observed in the sink. Mixtures of leaf-like material were also found in several bowls and pans. Subclavian blood screened positive for coniine by full-scan Gas Chromatography/Mass Spectrometry (GC/MS). Semi-quantitative confirmation testing was performed by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) and showed the presence of coniine at a concentration of 35 ng/mL. These analytical approaches can be used to substantiate or exclude poison hemlock exposure as a cause of death.

[Rhabdomyolysis: have you considered food poisoning from quails?]

Rhabdomyolysis (R) is a complex condition involving the rapid dissolution of damaged or injured skeletal muscle. This leads to the direct release of intracellular components, including myoglobin, creatine kinase, aldolase, and lactate dehydrogenase, as well as electrolytes, into the bloodstream and extracellular space. Clinically, R shows a triad of symptoms: myalgia, limb weakness, and myoglobinuria without hematuria, while myoglobin has been recognized as playing a part in the development of acute kidney injury. Coturnism is a relatively rare disease, mostly found in the European countries bordering the Mediterranean Sea, characterized by acute R. It follows the consumption of Coturnix coturnix, a species of quails common in Europe, that have ingested the toxic substances (and especially coniine) present in the herbaceous plant called hemlock (Conium maculatum). Coniine may be lethal at a dose of 150 mg but it has neurotoxic effects at smaller doses, with acute R and acute kidney injury. Freezing and cooking the meat does not inactivate the alkaloids present in the birds' flesh and digestive tract. The clinical course of coturnism includes neurotoxicosis, tremor, vomiting, muscle paralysis, respiratory paralysis/failure, R and acute kidney injury. In appropriate geographical and temporal settings, it should be considered when diagnosing patients with acute R. The genetic, biochemical and epidemiological characteristics of coturnism are not yet fully known, while we wait reliable data from experimental studies.

Conium maculatum intoxication: Literature review and case report on hemlock poisoning.

The aim of this paper is to highlight the symptomatology in three Conium maculatum intoxication incidents, one of which was fatal. A number of studies were reviewed in order to update and summarize the relevant literature on the incidence, sociodemographic variables, method of poisoning, pathophysiology, diagnosis, variables associated with survival and fatality, management, and treatment of C. maculatum intoxication as well as the biosynthesis and biological effects of poison hemlock alkaloids. Results show that hemlock poisoning is relatively rare, although incidence varies in different regions, despite its worldwide distribution. Hemlock poisoning is more common in European and especially Mediterranean countries. The majority of the patients are adult males over 38 years of age. The clinical course of hemlock poisoning includes neurotoxicosis, tremor, vomiting, muscle paralysis, respiratory paralysis/failure, rhabdomyolysis, and acute renal failure. The therapeutic management focuses on absorption reduction, close observation for complications, and supportive therapy (especially for respiration). Acute occurrence is severe and life-threatening, but the survival rate is high if treatment is provided promptly. Recovery is rapid, generally taking only a few days.

Polyketide synthases from poison hemlock (Conium maculatum L.).

Coniine is a toxic alkaloid, the biosynthesis of which is not well understood. A possible route, supported by evidence from labelling experiments, involves a polyketide formed by the condensation of one acetyl-CoA and three malonyl-CoAs catalysed by a polyketide synthase (PKS). We isolated PKS genes or their fragments from poison hemlock (Conium maculatum L.) by using random amplification of cDNA ends (RACE) and transcriptome analysis, and characterized three full-length enzymes by feeding different starter-CoAs in vitro. On the basis of our in vitro experiments, two of the three characterized PKS genes in poison hemlock encode chalcone synthases (CPKS1 and CPKS2), and one encodes a novel type of PKS (CPKS5). We show that CPKS5 kinetically favours butyryl-CoA as a starter-CoA in vitro. Our results suggest that CPKS5 is responsible for the initiation of coniine biosynthesis by catalysing the synthesis of the carbon backbone from one butyryl-CoA and two malonyl-CoAs.